Spray retention by foliar targets is influenced by both biological and rheological factors. Plant morphology (leaf surface-structure, degree of pubescence, leaf angle) combined with the spray liquid properties (surface tension, viscosity, droplet sizes, and velocities) all affect spray retention and subsequent deposit formation. Techniques used to explore these phenomena include on-demand droplet generators, high-speed movies and video-imaging. Maximum bubble pressure and oscillating jet technologies allow surface tension measurements to be made at droplet surface ages consistent with the impaction process. Judicious formulating and increased use of adjuvants has created many new opportunities for manipulating spray and deposit formation. However, recently proposed tactics advocating the use of coarse sprays to reduce drift have implications for pesticide targeting and subsequent pest control. This paper focuses on what has been learned about the phenomena of impaction, retention and deposit formation and suggests that while improved retention of pesticides by target plants is both practical and achievable, pesticide use rate reductions may not be so until the relationship between retention and efficacy is better understood.